In 1900, his name was presented to the National Convention at St. Louis, Missouri, as a candidate for vice-president. In 1902, the Chicago Chronicle said he was being groomed for president. "Bob Williams for President" headlined the Chicago Evening Post on November 9, 1903. In 1903, Illinois Democrats nominated Williams for the United States Senate. He did not win but received a letter from Williams Jennings Bryan, who expressed an interest in talking with him about plans for 1904. In 1904, he came in second place for the Democratic Vice Presidential nomination.

In 1904, Williams was defeated in his bid for reelection by Pleasant T. Chapman. After his term in the House of Representatives, he resumed the practice of his profession. He died in Loma Linda, California, November 8, 1923. He was interred in Maple Ridge Cemetery, Carmi, Illinois.